Democrat Hillary Clinton may not be the only presidential candidate with email server issues. Some of Donald Trump’s businesses are reportedly running insecure and outdated email servers. A security researcher has claimed that some “hotels and businesses” of Trump Organisation’s email servers are currently running on an outdated and unsupported version of Microsoft Windows Server, which also has limited security.

The Republican presidential candidate’s businesses are allegedly operating on the insecure email servers, which receive no new security patches, making them a prime target for hackers. According to security researcher Kevin Beaumont, who first uncovered the issue, numerous servers for Trump.org were found using outdated, unpatched and unsupported Windows server 2003, IIS 6.

“Running outdated software and operating systems for your publicly facing email infrastructure is problematic, especially when you’re a high-profile organisation,” Beaumont told Motherboard. “During an election where cybersecurity is such a big issue, I was a little amazed at what I saw.”

He added, “IIS is a webserver, and it’s particularly dangerous to run unpatched.”

Beaumont, who found the vulnerabilities examining public records, also noted that the Trump Orgnaisation’s email server uses only single factor authorisation. “Obviously, there is a lot more which could be looked into—but I’m just looking at publicly available information, I have no interest in accessing these systems,” he said.

A spokesperson of Trump Organisation said, “The Trump Organization deploys best in class firewall and anti-vulnerability technology with constant 24/7 monitoring. Our infrastructure is vast and leverages multiple platforms which are consistently monitored and upgraded using current cyber security best practices.”

Since revealing the Trump servers vulnerability on Twitter, Beaumont, a British citizen has been hounded on Twitter by Trump supporters, some of whom have even accused him of hacking into the servers. One Trump supporter claimed to have reported Beaumont to the FBI.